In the case of producing a compound in a catalytic gas-phase oxidation method such as a case of producing (meth)acrylic acid or the like from propane, propylene or isobutylene, a multi-tubular reaction apparatus has been conventionally used (refer to JP-A-2004-26799, for example). A usual multi-tubular reactor has a structure in which plural reaction tubes filled with a catalyst and plural baffle plates having an opening for spreading a heat medium led in a shell of the reactor all over the shell are interiorly provided in the shell of the reactor. In controlling an operation of the multi-tubular reactor, a temperature of the heat medium flowing in the shell is detected so that the temperature of the heat medium in the shell would be controlled to be uniform on the basis of a result of the detection, generally.
As a method for controlling the temperature of the heat medium to be uniform, generally adopted is a method in which a part of the heat medium is taken out outside the reactor, cooled so that the temperature of the heat medium at a predetermined measuring point, an outlet of a heat medium circulation pump, for example, would be constant, and then, returned to the reactor. In this case, it is required to control the external circulation flow of the heat medium when the cooling load is set to be constant while the cooling load of the heat medium should be controlled when the external circulation flow is set to be constant to the contrary.
There are problems, however, such that a runaway reaction is likely to be caused due to cooling not in time and that a hot spot is likely to cause a life of the catalyst to be deteriorated when the circulation amount is low and the reaction temperature rises in the case of changing the external circulation amount since the catalytic gas-phase oxidation reaction as described above is generally a largely exothermic reaction.
Further, in the case of changing the cooling load, control is carried out through many steps as follows. That is, the amount of cooling water in a heat exchanger is changed in accordance with an indication of a temperature controller, the change is transmitted to the heat medium, the heat medium is further fed to the heat medium circulation pump, and then, a temperature at a measuring point is changed. Accordingly, time delay in the control occurs easily, and thereby, so called overshoot, in which actual temperature changes, exceeding the set temperature, easily happens. This causes a problem of unstableness.